4bc600ff42
A long, long time ago, on a GET request, the proxy would go look on 3* nodes for the requested thing. If one of the primary nodes was error-limited, it'd look on two primaries and a handoff. Since this indicated some failure somewhere, the proxy would emit a warning: "Handoff requested (1)". If two primaries were down, there'd be a second message "Handoff requested (2)", and so on. Some StatsD messages were emitted too. A somewhat shorter time ago (commit d79a67eb), the proxy started looking into handoffs if it got 404s from the primaries. While this was a good idea, it resulted lots of "Handoff requested (N)" log spam; you'd see these messages on every single 404. Also, the StatsD handoff_count and handoff_all_count metrics shot way up and turned into noise. This commit restores the original intent (and usefulness) of the log messages and StatsD metrics: if the proxy only looks at the normal number of handoff nodes, nothing is logged. However, if a primary is down, then the message "Handoff requested (1)" will be logged, indicating that the proxy looked at one more handoff than it normally would, and this happened because a primary node was error-limited. Closes-Bug: 1297214 * or whatever the replica count was Change-Id: If1b77c18c880b096e8ab1df3008db40ce313835d
Swift
A distributed object storage system designed to scale from a single machine to thousands of servers. Swift is optimized for multi-tenancy and high concurrency. Swift is ideal for backups, web and mobile content, and any other unstructured data that can grow without bound.
Swift provides a simple, REST-based API fully documented at http://docs.openstack.org/.
Swift was originally developed as the basis for Rackspace's Cloud Files and was open-sourced in 2010 as part of the OpenStack project. It has since grown to include contributions from many companies and has spawned a thriving ecosystem of 3rd party tools. Swift's contributors are listed in the AUTHORS file.
Docs
To build documentation install sphinx (pip install sphinx), run
python setup.py build_sphinx, and then browse to /doc/build/html/index.html.
These docs are auto-generated after every commit and available online at
http://docs.openstack.org/developer/swift/.
For Developers
The best place to get started is the "SAIO - Swift All In One". This document will walk you through setting up a development cluster of Swift in a VM. The SAIO environment is ideal for running small-scale tests against swift and trying out new features and bug fixes.
You can run unit tests with .unittests and functional tests with
.functests.
Code Organization
- bin/: Executable scripts that are the processes run by the deployer
- doc/: Documentation
- etc/: Sample config files
- swift/: Core code
- account/: account server
- common/: code shared by different modules
- middleware/: "standard", officially-supported middleware
- ring/: code implementing Swift's ring
- container/: container server
- obj/: object server
- proxy/: proxy server
- test/: Unit and functional tests
Data Flow
Swift is a WSGI application and uses eventlet's WSGI server. After the
processes are running, the entry point for new requests is the Application
class in swift/proxy/server.py. From there, a controller is chosen, and the
request is processed. The proxy may choose to forward the request to a back-
end server. For example, the entry point for requests to the object server is
the ObjectController class in swift/obj/server.py.
For Deployers
Deployer docs are also available at http://docs.openstack.org/developer/swift/. A good starting point is at http://docs.openstack.org/developer/swift/deployment_guide.html
You can run functional tests against a swift cluster with .functests. These
functional tests require /etc/swift/test.conf to run. A sample config file
can be found in this source tree in test/sample.conf.
For Client Apps
For client applications, official Python language bindings are provided at http://github.com/openstack/python-swiftclient.
Complete API documentation at http://docs.openstack.org/api/openstack-object-storage/1.0/content/
For more information come hang out in #openstack-swift on freenode.
Thanks,
The Swift Development Team